The present invention relates to a metal detector for detecting metal objects according to the preamble of claim 1.
Metal detectors are used in numerous different fields and are based on the measurement of changes to the electromagnetic field, which are brought about by metal objects located in a zone to be monitored. Metal detectors are used in the security field, for checking passengers at airports and for checking visitors in particularly highly protected buildings or installations Metal detectors are also used for a wide range of purposes in industry.
DE-OS 32 28 447 discloses a metal detector for detecting metal objects, in which a field coil is excited in pulsed manner and the field influencing is determined and/or measured by two receiving coils connected back to back and a series-connected evaluation means. particularly when used in so-called door frames, through which pass the persons to be checked, a metal object to be detected can be either moved very closely passed the field coil or the receiving coils. However, as the sensitivity decreases with increasing distance from the receiving coils and reaches its minimum at the field coils in this arrangement, different test signals can occur in the receiving coils as a function of the position of the metal object.